The present invention relates to an apparatus and corresponding method for compressing image data, and an apparatus and method for increasing throughput of a processor involving additions, subtractions, and shifts.
The present invention is related to the above identified cross-referenced applications which are commonly owned by the same assignee as the present invention. The details of these cross-referenced applications are hereby incorporated by reference.
However, the aspects of the present invention are not limited to such image compression systems. Rather, the present invention is directed toward an apparatus and corresponding method for improving the throughput of a general data signal processing system, such as an acoustic data compression system.
In signal processing it is often necessary to perform time-consuming arithmetic. Today's general-purpose processors (such as the Motorola 68020) usually have 32-bit arithmetic data paths, but this is far more precision than is needed for important applications such as acoustic or image processing, such as with the present invention. It would be preferable to have less precision and more speed in such an acoustic or image processing environment.
For instance, the Generalized Chen Transform (GCT) described in the cross-referenced patent and patent applications may be implemented to perform an approximation to the discrete cosine transform (DCT) using only additions, subtractions and shifts, with a final multiply. An accuracy of 32-bits is not required to provide acceptable image quality. Therefore, the throughput of the GCT can be dramatically increased by combining two 16-bit words of data into each 32-bit word, processing the two 16-bit words in parallel in a 32-bit processor, and extracting two 16-bit words of output data. This process allows a single-instruction single-data (SISD) machine to operate as a single-instruction multiple-data (SIMD) machine.